1. Field of Invention
The present invention relates to a horn for a vehicle, and specifically to a horn that is mounted on a vehicle, such as an automobile or a motorcycle.
2. Description of Related Art
Some horns for vehicles have a structure in which a vibration generating member that includes an electromagnet is accommodated in a cylindrical case having a bottom, and sound is produced by vibrating a diaphragm formed integrally with the opening of the case in accordance with the vibration of the vibration generating part. In this type of horn for a vehicle, since the coil bobbin around which a coil is wound to form an electromagnet produces the vibration of the diaphragm, it is necessary to securely fix the coil bobbin to the bottom surface of the case. To achieve this, a conventional horn fixes the coil bobbin to the case by providing a plate fixed to the case at the surface on the case opening side of the coil bobbin as a bridge between the coil bobbin and the case. However, this creates a problem in that there is a need for a plate and for fixing members for fixing the coil bobbin to the case in at least two places, which results not only in an increase in the number of components, but also an increase in the number of operations necessary for assembly.
One proposed solution is to directly fix the coil bobbin to the case by caulking as proposed in, for example, JP-U-6-73799, which discloses a horn for a vehicle wherein a tightening part protrudes from a coil bobbin formed of a thermoplastic resin material, and wherein the tightening part is inserted into a through hole formed in the cylinder bottom part of the case so that the penetrating tip end thereof is heat-caulked outside the case, whereby members such as a plate and the like are unnecessary.
In the above-described conventional horn, the heat-caulked part of the coil bobbin is exposed. However, since the coil bobbin is formed of a resin material, the heat-caulked part can be damaged when hit by stones and the like. In order to avoid this, it is necessary for the horn to have a structure so as to protect the heat-caulked part by a stay for supporting and fixing the horn on a car frame (car body). If this is done, however, a problem arises in that the surface-to-surface contact structure between the case bottom part and the stay becomes inadequate, resulting in a decrease in strength of the horn. Furthermore, in this case, it is necessary to increase the strength of the flange part of the protruding tightening part side to strongly fix the bobbin itself to the case. In order to do this, the flange part where the tightening part is formed should be thick-walled. However, this creates a problem in that the coil winding part of the coil bobbin would shift toward the opening side by the increment of the thickness of wall, whereby the horn would increase in thickness, leading to an overall increase in the size thereof. This is one of the problems that the present invention aims to solve.
Also, such a horn for a vehicle produces sound by forcing a diaphragm to vibrate, and since, if a difference in pressure occurs between the inside and outside of the case, the smooth vibration of the diaphragm is impaired, producing a unstable production of sound. In order to avoid this, it is necessary to add a ventilation hole to equalize the pressure between the interior and the exterior. This raises another issue of complicating manufacturing, which is another of the problems that the present invention aims to solve.